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Merge pull request #198 from est31/master

Partial revert of the float conversion refactor in #192
master
Alex Crichton 4 years ago
committed by GitHub
parent
commit
0b9844764e
  1. 261
      src/float/conv.rs

261
src/float/conv.rs

@ -1,87 +1,83 @@
use float::Float;
use int::{Int, CastInto};
fn int_to_float<I: Int, F: Float>(i: I) -> F where
F::Int: CastInto<u32>,
F::Int: CastInto<I>,
I::UnsignedInt: CastInto<F::Int>,
u32: CastInto<F::Int>,
{
if i == I::ZERO {
return F::ZERO;
}
use int::Int;
let two = I::UnsignedInt::ONE + I::UnsignedInt::ONE;
let four = two + two;
let mant_dig = F::SIGNIFICAND_BITS + 1;
let exponent_bias = F::EXPONENT_BIAS;
macro_rules! int_to_float {
($i:expr, $ity:ty, $fty:ty) => ({
let i = $i;
if i == 0 {
return 0.0
}
let n = I::BITS;
let (s, a) = i.extract_sign();
let mut a = a;
let mant_dig = <$fty>::SIGNIFICAND_BITS + 1;
let exponent_bias = <$fty>::EXPONENT_BIAS;
// number of significant digits
let sd = n - a.leading_zeros();
let n = <$ity>::BITS;
let (s, a) = i.extract_sign();
let mut a = a;
// exponent
let mut e = sd - 1;
// number of significant digits
let sd = n - a.leading_zeros();
if I::BITS < mant_dig {
return F::from_parts(s,
(e + exponent_bias).cast(),
a.cast() << (mant_dig - e - 1));
}
// exponent
let mut e = sd - 1;
if <$ity>::BITS < mant_dig {
return <$fty>::from_parts(s,
(e + exponent_bias) as <$fty as Float>::Int,
(a as <$fty as Float>::Int) << (mant_dig - e - 1))
}
a = if sd > mant_dig {
/* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
* finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
* 12345678901234567890123456
* 1 = msb 1 bit
* P = bit MANT_DIG-1 bits to the right of 1
* Q = bit MANT_DIG bits to the right of 1
* R = "or" of all bits to the right of Q
*/
let mant_dig_plus_one = mant_dig + 1;
let mant_dig_plus_two = mant_dig + 2;
a = if sd == mant_dig_plus_one {
a << 1
} else if sd == mant_dig_plus_two {
a = if sd > mant_dig {
/* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
* finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
* 12345678901234567890123456
* 1 = msb 1 bit
* P = bit MANT_DIG-1 bits to the right of 1
* Q = bit MANT_DIG bits to the right of 1
* R = "or" of all bits to the right of Q
*/
let mant_dig_plus_one = mant_dig + 1;
let mant_dig_plus_two = mant_dig + 2;
a = if sd == mant_dig_plus_one {
a << 1
} else if sd == mant_dig_plus_two {
a
} else {
(a >> (sd - mant_dig_plus_two)) as <$ity as Int>::UnsignedInt |
((a & <$ity as Int>::UnsignedInt::max_value()).wrapping_shl((n + mant_dig_plus_two) - sd) != 0) as <$ity as Int>::UnsignedInt
};
/* finish: */
a |= ((a & 4) != 0) as <$ity as Int>::UnsignedInt; /* Or P into R */
a += 1; /* round - this step may add a significant bit */
a >>= 2; /* dump Q and R */
/* a is now rounded to mant_dig or mant_dig+1 bits */
if (a & (1 << mant_dig)) != 0 {
a >>= 1; e += 1;
}
a
/* a is now rounded to mant_dig bits */
} else {
(a >> (sd - mant_dig_plus_two)) |
Int::from_bool((a & I::UnsignedInt::max_value()).wrapping_shl((n + mant_dig_plus_two) - sd) != Int::ZERO)
a.wrapping_shl(mant_dig - sd)
/* a is now rounded to mant_dig bits */
};
/* finish: */
a |= Int::from_bool((a & four) != I::UnsignedInt::ZERO); /* Or P into R */
a += Int::ONE; /* round - this step may add a significant bit */
a >>= 2; /* dump Q and R */
/* a is now rounded to mant_dig or mant_dig+1 bits */
if (a & (I::UnsignedInt::ONE << mant_dig)) != Int::ZERO {
a >>= 1; e += 1;
}
a
/* a is now rounded to mant_dig bits */
} else {
a.wrapping_shl(mant_dig - sd)
/* a is now rounded to mant_dig bits */
};
F::from_parts(s,
(e + exponent_bias).cast(),
a.cast())
<$fty>::from_parts(s,
(e + exponent_bias) as <$fty as Float>::Int,
a as <$fty as Float>::Int)
})
}
intrinsics! {
#[arm_aeabi_alias = __aeabi_i2f]
pub extern "C" fn __floatsisf(i: i32) -> f32 {
int_to_float(i)
int_to_float!(i, i32, f32)
}
#[arm_aeabi_alias = __aeabi_i2d]
pub extern "C" fn __floatsidf(i: i32) -> f64 {
int_to_float(i)
int_to_float!(i, i32, f64)
}
#[use_c_shim_if(all(target_arch = "x86", not(target_env = "msvc")))]
@ -92,28 +88,28 @@ intrinsics! {
if cfg!(target_arch = "x86_64") {
i as f64
} else {
int_to_float(i)
int_to_float!(i, i64, f64)
}
}
#[unadjusted_on_win64]
pub extern "C" fn __floattisf(i: i128) -> f32 {
int_to_float(i)
int_to_float!(i, i128, f32)
}
#[unadjusted_on_win64]
pub extern "C" fn __floattidf(i: i128) -> f64 {
int_to_float(i)
int_to_float!(i, i128, f64)
}
#[arm_aeabi_alias = __aeabi_ui2f]
pub extern "C" fn __floatunsisf(i: u32) -> f32 {
int_to_float(i)
int_to_float!(i, u32, f32)
}
#[arm_aeabi_alias = __aeabi_ui2d]
pub extern "C" fn __floatunsidf(i: u32) -> f64 {
int_to_float(i)
int_to_float!(i, u32, f64)
}
#[use_c_shim_if(all(not(target_env = "msvc"),
@ -121,17 +117,17 @@ intrinsics! {
all(not(windows), target_arch = "x86_64"))))]
#[arm_aeabi_alias = __aeabi_ul2d]
pub extern "C" fn __floatundidf(i: u64) -> f64 {
int_to_float(i)
int_to_float!(i, u64, f64)
}
#[unadjusted_on_win64]
pub extern "C" fn __floatuntisf(i: u128) -> f32 {
int_to_float(i)
int_to_float!(i, u128, f32)
}
#[unadjusted_on_win64]
pub extern "C" fn __floatuntidf(i: u128) -> f64 {
int_to_float(i)
int_to_float!(i, u128, f64)
}
}
@ -141,116 +137,115 @@ enum Sign {
Negative
}
fn float_to_int<F: Float, I: Int>(f: F) -> I where
F::Int: CastInto<u32>,
F::Int: CastInto<I>,
{
let f = f;
let fixint_min = I::min_value();
let fixint_max = I::max_value();
let fixint_bits = I::BITS;
let fixint_unsigned = fixint_min == I::ZERO;
let sign_bit = F::SIGN_MASK;
let significand_bits = F::SIGNIFICAND_BITS;
let exponent_bias = F::EXPONENT_BIAS;
//let exponent_max = F::exponent_max() as usize;
// Break a into sign, exponent, significand
let a_rep = F::repr(f);
let a_abs = a_rep & !sign_bit;
// this is used to work around -1 not being available for unsigned
let sign = if (a_rep & sign_bit) == F::Int::ZERO { Sign::Positive } else { Sign::Negative };
let mut exponent: u32 = (a_abs >> significand_bits).cast();
let significand = (a_abs & F::SIGNIFICAND_MASK) | F::IMPLICIT_BIT;
// if < 1 or unsigned & negative
if exponent < exponent_bias ||
fixint_unsigned && sign == Sign::Negative {
return I::ZERO;
}
exponent -= exponent_bias;
macro_rules! float_to_int {
($f:expr, $fty:ty, $ity:ty) => ({
let f = $f;
let fixint_min = <$ity>::min_value();
let fixint_max = <$ity>::max_value();
let fixint_bits = <$ity>::BITS as usize;
let fixint_unsigned = fixint_min == 0;
let sign_bit = <$fty>::SIGN_MASK;
let significand_bits = <$fty>::SIGNIFICAND_BITS as usize;
let exponent_bias = <$fty>::EXPONENT_BIAS as usize;
//let exponent_max = <$fty>::exponent_max() as usize;
// Break a into sign, exponent, significand
let a_rep = <$fty>::repr(f);
let a_abs = a_rep & !sign_bit;
// this is used to work around -1 not being available for unsigned
let sign = if (a_rep & sign_bit) == 0 { Sign::Positive } else { Sign::Negative };
let mut exponent = (a_abs >> significand_bits) as usize;
let significand = (a_abs & <$fty>::SIGNIFICAND_MASK) | <$fty>::IMPLICIT_BIT;
// if < 1 or unsigned & negative
if exponent < exponent_bias ||
fixint_unsigned && sign == Sign::Negative {
return 0
}
exponent -= exponent_bias;
// If the value is infinity, saturate.
// If the value is too large for the integer type, 0.
if exponent >= (if fixint_unsigned {fixint_bits} else {fixint_bits -1}) {
return if sign == Sign::Positive {fixint_max} else {fixint_min}
}
// If 0 <= exponent < significand_bits, right shift to get the result.
// Otherwise, shift left.
// (sign - 1) will never overflow as negative signs are already returned as 0 for unsigned
let r: I = if exponent < significand_bits {
(significand >> (significand_bits - exponent)).cast()
} else {
(significand << (exponent - significand_bits)).cast()
};
if sign == Sign::Negative {
(!r).wrapping_add(I::ONE)
} else {
r
}
// If the value is infinity, saturate.
// If the value is too large for the integer type, 0.
if exponent >= (if fixint_unsigned {fixint_bits} else {fixint_bits -1}) {
return if sign == Sign::Positive {fixint_max} else {fixint_min}
}
// If 0 <= exponent < significand_bits, right shift to get the result.
// Otherwise, shift left.
// (sign - 1) will never overflow as negative signs are already returned as 0 for unsigned
let r = if exponent < significand_bits {
(significand >> (significand_bits - exponent)) as $ity
} else {
(significand as $ity) << (exponent - significand_bits)
};
if sign == Sign::Negative {
(!r).wrapping_add(1)
} else {
r
}
})
}
intrinsics! {
#[arm_aeabi_alias = __aeabi_f2iz]
pub extern "C" fn __fixsfsi(f: f32) -> i32 {
float_to_int(f)
float_to_int!(f, f32, i32)
}
#[arm_aeabi_alias = __aeabi_f2lz]
pub extern "C" fn __fixsfdi(f: f32) -> i64 {
float_to_int(f)
float_to_int!(f, f32, i64)
}
#[unadjusted_on_win64]
pub extern "C" fn __fixsfti(f: f32) -> i128 {
float_to_int(f)
float_to_int!(f, f32, i128)
}
#[arm_aeabi_alias = __aeabi_d2iz]
pub extern "C" fn __fixdfsi(f: f64) -> i32 {
float_to_int(f)
float_to_int!(f, f64, i32)
}
#[arm_aeabi_alias = __aeabi_d2lz]
pub extern "C" fn __fixdfdi(f: f64) -> i64 {
float_to_int(f)
float_to_int!(f, f64, i64)
}
#[unadjusted_on_win64]
pub extern "C" fn __fixdfti(f: f64) -> i128 {
float_to_int(f)
float_to_int!(f, f64, i128)
}
#[arm_aeabi_alias = __aeabi_f2uiz]
pub extern "C" fn __fixunssfsi(f: f32) -> u32 {
float_to_int(f)
float_to_int!(f, f32, u32)
}
#[arm_aeabi_alias = __aeabi_f2ulz]
pub extern "C" fn __fixunssfdi(f: f32) -> u64 {
float_to_int(f)
float_to_int!(f, f32, u64)
}
#[unadjusted_on_win64]
pub extern "C" fn __fixunssfti(f: f32) -> u128 {
float_to_int(f)
float_to_int!(f, f32, u128)
}
#[arm_aeabi_alias = __aeabi_d2uiz]
pub extern "C" fn __fixunsdfsi(f: f64) -> u32 {
float_to_int(f)
float_to_int!(f, f64, u32)
}
#[arm_aeabi_alias = __aeabi_d2ulz]
pub extern "C" fn __fixunsdfdi(f: f64) -> u64 {
float_to_int(f)
float_to_int!(f, f64, u64)
}
#[unadjusted_on_win64]
pub extern "C" fn __fixunsdfti(f: f64) -> u128 {
float_to_int(f)
float_to_int!(f, f64, u128)
}
}
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